Caterpillar C15 Repower: Review

This 1995 Western Star 4964F is owned by CR & S Jones, of Scottsdale Tasmania, their fleet of modern trucks transport timber products around the island as well as local ports for export to the mainland.

The 4964F was purchased second hand over a decade and half ago, and has clocked up well over three million kilometres. In that time, it has had a few modifications and updates. Today its primary role in the fleet is the ‘spare truck’ and it’s kept in top condition, ready to go to work whenever it’s needed.

Back in 1995 when it arrived in Australia, it was powered by a Caterpillar 3406E rated at 455hp (339kW) at 2100rpm and developed 1650 lb-ft (2237Nm) at 1200rpm. The transmission was an RTLO16718B 18-speed that delivered the power to a pair of Rockwell RT46-160 with a final drive ratio of 4.10:1 which rode on Hendrickson HAS400 air suspension.

Today, the wick has been turned up a little since the C15 was slotted in where the old 3406E once resided. Power output has increased 100hp to 550 (410 kW) and a torque increase of 200 lb-ft to 1850 lb-ft (2508Nm) at 1200rpm.

Needless to say, the transmission needed upgrading to handle the additional torque, and an RTLO20918B was bolted up to the C15. The Rockwell rear axles were retained along with the 4.10:1 ratio which has the Heritage running in the engine’s sweet spot of 1650rpm at 100km/h.

Hendrickson HAS style suspensions are fine for light-duty applications, but they are prone to axle tramp. This suspension is also susceptible to axle hang up and loss of traction even when driving through driveways.

Consequently, the Hendrickson was removed and was upgraded to an Airliner suspension to ensure the power was firmly planted on the ground.

Commercial production of the Caterpillar C15 on-road engine commenced in 1999 and ceased in 2007. Rumour has it that the earlier engines with 6NZ prefix in the serial number were the pick of the bunch.

The C15 had a single turbocharger with simple electronics and weighed less than its predecessor the 3406E. However, from a parts perspective there is good news, many components are interchangeable between the 3406E, C15 and ACERT engines. Nevertheless, there are subtle distinctions between each engine variant and it’s well worth while exploring the differences.

Part of the design criteria for the C15 was to improve on the 3406E design and reduce oil leakage issues that plagued the older model. They achieved this with the introduction of relief slots in the bottom of the cylinder head that kept the head gaskets from getting crushed. However, many technicians have noted that it pays to use quality replacement head gaskets on the C15 to ensure no oil leaks.

But it’s wasn’t all plain sailing for the C15, the transition to the next emissions standards, meant Caterpillar built what became known as ‘Bridge’ engines in the production year of 2002 to 2003 before the introduction of the C15 ACERT.

These ‘Bridge’ engines lacked the renowned performance of the original C15, experienced high exhaust temperatures and suffered from terrible fuel economy. The good news story here is that ECM updates quickly rectified many of the issues.

But don’t let the nomenclature of the C15 ACERT fool you. For a long time, people thought the ACERT suffix to the C15 indicated the addition of the second turbocharger, but that’s far from true. From a hardware point of view, the ACERT engine has a one-piece steel piston opposed to the C15’s two-piece aluminium skirt piston design. The stroke of the ACERT is the same as the C16 and there is an entirely new emission technology that ACERT draws its name from.

Nevertheless, the good news is that when an engine has been on the market as long as the C15 there is a wide selection of quality aftermarket parts readily available that help improve the durability, performance and economy of the C15. For instance, pistons with graphite coating, rods and main bearings constructed from tri-metal blend and induction-hardened cylinder liners, all to increase durability are common upgrades.

How does the C15 work out on the road? There was only one way to find out and that was climb into the cabin for a week and do the job it was built to do.

Day One was an early start, the big yellow engine under the hood cranked into life right on 3:00am. In the cool morning stillness, the turbo gulped in loads of chilled air, the result was astonishing torque as the Heritage climbed up over the mountain range on the way south. Coupled behind, the tautliner was stacked to the roof with new pallets, not the heaviest load, but a good load nonetheless.

Day Two’s assignment was a load of timber to the west coast on a drop deck. Again, the C15 powered Heritage made light work of the load behind.

For the rest of the week, the Heritage was connected to the walking floor ‘Chipliner’ which had the gross weight up to 45.5 tonne, something for the C15 to really get its teeth into. Handling wise, the Airliner suspension upgrade really gives the Heritage sure footing and that’s something you need on the twisting undulating rural countryside of northern Tasmania. Performance wise the C15 certainly has all 550 horses and they’re big hearted Clydesdales too.

The engine upgrade has given this old highway hauler a new lease of life, from an economic perspective, the C15’s proven performance and durability make it a sound investment.

Economy wise, the C15 can be a little thirsty if driven too hard, but if you let the big Cat do its thing you can achieve fuel economy that matches today’s modern engines. Our economy for the first two days with the lighter loads and longer highway runs averaged 2.25km/l, and on the heavy loads in the hilly country 1.8 – 1.9km/l which included 30 minutes PTO time (per shift) operating the walking floor to unload.

When it comes to repowering an older truck with a C15, it’s an easier task if the original engine was CAT, because the engine mounts and wiring mean you can virtually drop the C15 straight in. On the other hand, if you’re switching out a different engine, be prepared to do a little more work slot in the C15.

But it’s well worth talking to your accountant to discuss the best options to suit your particular business operation before rushing into the repower option and do your homework on the warranty of the installation.

Trucksales would like to thank CR and S Jones for the assistance compiling this article.

1995 Western Star 4964F Specs – Kilometres 3-million
Engine: Caterpillar C15
Horsepower: 550hp (410kW) at 2100RPM
Torque: 1850 lbft (2508Nm) at 1200RPM
Air-Cleaner: Dual 14” Donaldson
Transmission: Eaton RTLO20918B 18-speed
Clutch: Spicer 15 ½” Super Damp
Front Axle: Rockwell FG941
Front Suspension: Multi Leaf
Steering: Ross TAS-85
Rear Axles: Rockwell RT46-160
Ratio: 4.10:1
Brakes: S-cam
Rear Suspension: Airliner 46K
Front Wheels: 10-Stud (385/65R)
Rear Wheels: 10-Stud
Extras: Polished stainless tank wrap, polished alloy bullbar, chrome bug deflector, Powerdown shockers, alloy chassis deck plate, hydraulics